The development of high-brightness solid state light sources has led to use of such devices in various lighting fixtures. In general, a solid state light source operates in a fundamentally different way than an incandescent lamp or a gas discharge lamp, and therefore may not be connectable to conventional lighting fixtures designed for such conventional light sources. A driver circuit may be used, however, to allow use of a lamp including solid state light sources as a retrofit for conventional lighting fixtures. A driver circuit for a solid state light source typically converts an alternating current (AC) input, such as a 120V/60 Hz line input or input from a dimmer switch, to a stable direct current (DC) voltage, which is used to drive the solid state light source. Such a circuit typically incorporates a rectifier, which receives the AC input, and a switching converter circuit. The switching converter circuit receives a rectified AC output from the rectifier, and provides a stable, regulated DC output to the solid state light source.
A variety of switching converter circuit configurations are well-known in the art. Certain types of switching converter circuits include known configurations, such as buck converters, boost converters, buck-boost converters, etc., which are generally categorized as switching regulators. These devices include a switch, e.g. a transistor, which is selectively operated to allow energy to be stored in an energy storage device, e.g. an inductor, and then transferred to one or more filter capacitors. The filter capacitor(s) provide a relatively smooth DC output voltage to the load and provide essentially continuous energy to the load between energy storage cycles.
Another known type of switching converter includes a transformer-based switching regulator, such as a “flyback” converter. In a transformer-based switching regulator, the primary side of the transformer is coupled to the rectified AC output of the rectifier. The regulated DC output voltage is provided at the secondary side of the transformer, which is electrically isolated from the primary side of the transformer.